According to the latest rumor from CR1, Canon is working on a new Ultra Wide Angle Zoom Lens to replace the current EF 16-35mm F2.8L II USM lens, which was released in 2007.
Canon announced the EF 11-24mm F4L USM lens this year. It is an excellent wide angle lens, but it is much heavier and more expensive. So this new cheaper and lighter version is required by a lot of event photographers. It is rumored the focal length will change slightly to 15-35mm and will be announced after the release of Canon EF 35mm F1.4L II lens.
Source: CR1
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